Interoffice connection



Sept, 27, 1949- K. BURGENER INTERQFFICE CONNECTION Fild Sept. 15, 1945 '3 Sheets-Sheet 2 INVENTOR. KARL L. B URGENER ATTORNEY P 1949- K. L. B URGENER 2,483,179

INTEROFFICE CQNNECTION Filed Sept. 15, 1945 s sheets-sheet s CALLING DEVICE COMMON EQUIP.

' IN VEN TOR.

KARL L. BURGBIER ATTORNEY trunk circuits such as trunk J. The switchboard Y is equipped with a plurality of cord circuits such as cord circuit K, and a plurality of terminating circuits for lines one of which is shown at N and is suitable for use as a common battery line, another, shown at P, is suitable for use as a magneto or toll line, and still another, shown at R, is suitable for connection to an automatic switchboard for outgoing service. The lines N and P can be connected to a subscriber's substation or other equipment suitable for use thereon over the conductors N and N and P and 1? respectively. The line R can be terminated on an automatic switch which may be aline switch, a selector or a connector similar to those shown on Fig. l. The switchboard Y may have more than one operators position in which case the terminating equipment for trunk circuit J and line circuits N, P, and R will be multipled throughout the board s"that it is accessible to each operators position. The cord circuits, such as cord K, in a position are arranged for connection to operators equipment common to the position as shown in Fig. 4, comprising an operators telephone M, a calling device S and other apparatus which cooperates with the apparatus in the cord circuits, such as cord circuit K, and enables the operator to perform the necessary operations for establishing connections.

The subscribers lines, such as line I in Fig. 1, extend between subscribers substations such as substation A and line switches in units such as LSU, and are multipled to connectors, such as the connector CONN. The line switches included in the units LSU may be of any desired type although preferably they are of the plunger or rotary type having their banks multipled together in groups and connected over trunk lines such as that indicated at 4 to selector switches such as the selector SEL.

The selectors, such as SEL are preferably of the well known Strowger type such as described in Patent 2,189,400, granted February 6, 1940, to Clarence E. Lomax and Pier Bakker, and are accessible to the line switches in the units LSU and also to the line switches such as LS which are associated with outgoing trunks such as trunk E. The selectors have access to connectors, such as connector CONN, and to incoming trunks, such as trunk D.

The connectors, such as connector CONN, are preferably of the well known Strowger vertical and rotary type such as described in Patent 2,040,153, granted May 12, 1936, to Seth Peterson, and have access to subscribers lines such as the line I. In the present case connectors, such as CONN, are accessible to calling subscribers, such as the subscriber at substation A, by way of their individual lines, such as line I, their individual line switches in units such as LSU, trunk lines such as that indicated at 4, and selectors such as SEL. The connector CONN is arranged to test a line to which it has been connected to determine whetherthe line is busy or free. If the line is busy the connector returns a distinctive tone, commonly known as busy tone, to the calling line. If the line is free the connector automatically signals the called line and returns a distinctive tone, commonly known as ring back tone to the calling line.

The line switches, selectors and connectors are controlled by subscribers by means of substations, such as A, which are equipped with calling devices and permit subscribers to establish connections directly with subscribers at substations such 4 as B. The operation of the automatic switches when used for establishing connections between subscriber lines is well known and does not form a part of this invention. It will, therefore, not be described.

The incoming trunks, such as trunk D, are associated with an operator attended switchboard X where they terminate on connecting keys, such as the key M0, in connecting link circuits. While only one connecting key I40 is shown an identical key is provided for the trunk D in each connecting link and the leads of the trunk are multipled to each of the keys. The line lamp I82 is a part of the incoming trunk D and is lighted when the trunk has been seized by a selector, such as SEL, to signal the operator. The switchboard X is accessible to subscribers substations such as substation A, by way of the line switch in unit LSU individual to the line I, selectors such as SEL, and incoming trunks such as D. The incoming trunk D is also connected to the two way trunk circuit J, Fig. 2, and to the line switch LS by means of the key 265 and the relay 2). The operation of the key 265 which is preferably mounted in the switchboard will automatically extend calls routed to the trunk D to the two way trunk J and will light the lamp 295 associated with terminating equipment for the trunk J at switchboard Y. The connection to the line switch LS through spring 266 and lead I5 prevents interference by the line switch with calls automatically extended from trunk D to trunk J.

There is a plurality of incoming trunks such as D in the switchboard X, each trunk having a connecting key such as key I40 in each of the links, and each trunk having a line lamp such as lamp I82.

The outgoing trunks, such as trunk E, are associated with the switchboard X where they terminate on connecting keys, such as key I10. An identical key is provided for trunk E in each connecting link and the trunk leads are multiplecl to each of the keys. The outgoing trunks extend to line switches, such as line switch LS, which is identical to the line switches in the units LSU and may be in one of the LSU units. The line switches, such as LS, have access to the selectors, such as SEL, and through the selectors and connectors, such as connector CONN, to subscriber substations such as substation A. A call ing device H can be connected to the outgoing trunks through a dialing key such as key I60. The outgoing trunks thus make subscribers substations, such as substation A, accessible to the switchboard X. The outgoing trunk E is also connected to the two way trunk J, Fig. 2, by means of the key 255. The operation of the key 255 automatically extends calls routed from switchboard Y over trunk J to one of the selectors, such ,as selector SEL, by means of the line switch LS. The connection from the line switch LS over lead I5 and spring 286 to the trunk D prevents interference by the trunk D with connec tions automatically extended from trunk J to a selector such as SEL.

There is a plurality of outgoing trunks such as E in the switchboard X, each trunk having a connecting key such as key I10 in each of the links, and each trunk having a dialing key such as key I50 and extending to a line switch such as the line switch LS.

The two way trunks such as trunk J terminate on connecting keys such as key 250. An identical key is provided for trunk J in each connecting link and the trunk leads are multipledto each key: h trunks ext ndpver;condilctorscsuchiasi 403 and 41. to a;v distant switchboaldJwhere; they: terminate on. iacksisu h: as-Jach; 553: Th line; lamp ZTIE'ispart: of; he wo way trunkvJ and-Lin; case key 255 is normal,..is; li hted whenthe trun J; is seized-atswitchbmrdf tosignalthe open-- atorc at switchboard X. The.;gllardj lamp 2;? 3 is; also nartof the-trunk. J; andis 1i h ed:aft r: he operator at, switchboard. Xdisconnects, by rem storinsgthe onn ng; key, s h as: key: fi0,-,aud;. remains lighted until; the trunk; J I is, released; at the switchboard Y. The two waytrunk J is con nec d: to outgoi g trunk E and: o; inc ming; trunk. D by; means of the key; 26: 5 and; the relay" 2.10.- The operationofthekey 2,65; automatically extends conne ions originatin ihesw tche boardv and routedover trunk, J, to selectors; such as SEL, by means of the line switch-LSsand; automaticallyextends;calls; routed from seiectors; tolincoming trunk D over trunkgJ tothe switchbQEtI'diY. The two way trunks are equipped with line lamps, such as lamp 295, at switchboard Y- which are lighted to signal the opfilfatolfvthereat,

when connections. are; routed either from; switchboardXgor-yfroin selectors such; as S-EL over thetwo 1-way trunks ,to switchboardgY,

There isa plurality of: two Way trunks, suehas; trunl ;J intthe switchboard X, eachgtrunkhaving azconnecting key such as key, 25 Bin each link; and eachtrunk having; a linelamp such s, lamp 112, aguard lampisuch aslamp 2113; and, aswitching key such as key 265. The switching keys, suchas key-265, associate-each offthe two way trunks with individual ones:.of the incoming trunks, such; as trunk D and with individual ones: of;-the outgoinggtrunks such as trunk-E.- At the switchboard Y 'each two sway-trunk terminatesaon a jack; such as jack 2%, and is equippedwitha line lamp suchzas lamp 295, If the switchboard Y hasv more; than one operatorsposition-the jack 290 and the lamp 255.1are multipledto other identical jacks-and lamps which aredistributed throughout the switchboardso that each operator-will. have-access; to the two way trunks by means-of cord-,circuits such as cordK.

The link circuits in theswitchboard X-have. connecting keyssuch as the key Mlllforeachincoming trunk, such as trunk D,- in eachlink, connectin keys such as the key llflgfor each out.- goingtrnnk, such as trunk-E, in eachalink and; connecting keys such as the keyifill for; eachtwowaytrunk, such as .trunk J; ineach link, anda; talkkey such as key I98, alocalisupervisorylamp such aslamp I81, and a'trunk supervisory lamp; such as 2H-in each link. Leads suchas Z'I and; 28;:are multipled to-each of the connecting keys, in: an individual link. while theleads from the trunks: are multipled to each of. the-connecting: eys-foran individual trunkv in eachlink. Thekeysldd, are, zfioand l9lliare a part ofsone link andgby means of them, the automatic switches, andtrunksD and E, connections maybeflestab lished between subscriberssubstations, such as substation A and the two .way trunk J. 'Thenkey Ifillcprovides a connection to the operators te1e- The-trunkingandswitchingarrangements-dc phone G so that the operator may perform the necessary services .in efiecting the connection.

The operators telephone, G, may be of any well known type having the usual'talking-instru-o Inentalities and alocal'batteryfeed. Ihe operatorfstelephone is connected to talk, key I90 over leads tl and 32 andythese leads are multipled toidentical talk keys ;,in;each;-link.

h uxiliary isnal' circuit; upplies battery:

tog he lampsi I 8!; I 8 11 :and-.,-2;12;'andaiteiszmule 5? iii.

tipledrto rail lamps in: the: switchboard X.'.

It is provided with a key by means of whichcthew connection. with common battery lines, suchyas;

theiline N; and; -magnetoor toll 1 lines; such as the; line P; as well as with two; way-trunks, sucln-as;- thetrunk-J; The; cordis-also arranged fonconnection; to: an automatic sW-itchhoard; The in comin trunks from a, local automatic: switche baardiwhich :a-re notshown are answered with the; plugcsfil sandiarrangedrso that'the cord functions, the same-.asrwhenitheplug 33 l. is used'with comlnonibatteryiline In extending calls tea-local;

automatic 1 exchange-the plug 39:1, is ;used,in. a; trunk such as the -tru nk;R. The plug 3-,8zl is use for. answering calls onitwo' wayztiunks; suchuas; trunk .J,, and-.xthe plug 391 is. used; for extending: CZJISJ'OVGI; such: trunks;

Thexcommon equipment, N, connects to cord: circuits;v suchas cord-:K; throughtalk keys, such. as key 376, in cooperation with relays such as; relay 35th through monitor; keys,- suchas-key 383,

and :tthriough combined -splitting; and dialirig re lays such-asirelayl-3l 0; The operatorfstelephone,

M issimilanto operators telephone, G; andyhas,

in additiona busy testw feature-which provides-a1, tip busy test from-t the plug, 397: The calling ,de-. vic.e,=.S, is: similar-to thecalling device; H; and: has in addition aicontrol lead=which is grounded, wher the :ca'lling device is oil. normal to-..operaterelays 44B and 43.0: and automatically connect: the i calling; device. t0-. any cord circuit in which thekey 310 and therelay; 350'-are operated;

'Iihe switchboard Ymay be aiswitchboard' ar-. rangediforwtoll .andlocal service in a manual :'sys-. temtand connecting withdistant automatic eX---- changes over two way trunks 1 such. astrunk J3. T-hG-SWitCYIbQaIdSM at the distant automatic ex i changes, such as switchboard 1X; provide a means; for relieving the operatorsat the switchboard Y of: such duties. as recording, information and; dialing when the exchangeloadis high and" means of: switching keys such as key 265 for,

permitting; the operators at switchboard Y: to. performkall these services for the automatic exa. changes-. when theexchange load is' light; Theea switchboard Ymay be a toll andspecialservica board associated withv an: automatic exchange whichis arranged for connection to-other auto-v matic exchanges equipped withswitchboards such as. switchboard I X;

scribed above are particularly useful in systems:- where charges -.are made-on all interoffice calls;- They can also be usedtoprovide full service to. as connectingex-change for alliofi'the lines in a: aprivatesautomaticbranch exchange without services;:of1'a full time attendantIati-the private ex-- change; It;;will:be understood, however, that-they above described arrangements are by; way, often-l amnlemnlyandathat: various modifications-may; besma'de in the circuit: detailscby those skilled in:

the art without departing from the spirit of the invention.

Having indicated the scope of my invention in general, I will now proceed to explain the operation of the particular embodiment thereof which I have shown in the drawings. For this purpose it will be assumed that both switchboards are attended and that the subscriber at substation A, Fig. 1, desires to obtain connection with the switchboard Y.

When the receiver is removed at the substation A on line I, Fig. 1, the associated line switch eX- tends the line to a selector in the well known manner. The subscriber then operates the calling device at the substation A causing the selector to step its wipers to the bank level assooiated with the incoming trunks, such as trunk D. Assuming that trunk D is the first idle incoming trunk the selector will connect the substation A to trunk D over leads I and H closing a circuit to the relay Hi! from ground through its upper. winding, lead I0, over the line I, lead II, through its lower winding to battery.

The relay Ill] operates armature III closing a circuit to relay I29 and operates armature H2 closing a circuit from ground through armature I33, lam=p I82, and lead-33, to battery in the auxiliary signal circuit, F. The lamp I82 lights indicating that a call is waiting on trunk D. The relay I operates and connects ground to lead I2 at armature I23 to hold the calling switch train. The functions of the other arm'atures of the relay I2ll which also operate at this time will be explained later.

The operator at the switchboard X answers by operating a connecting key and a talk key associated with one of the connecting links in the switchboard. Assuming that the operator answers on the link associated with key I40, Fig. 1, the key Hill is operated. Relay I is operated from ground at spring IAI. The relay I39 opens the circuit to the lamp I82 at armature I33, connects ground to the lead I2 at armature I34, and closes a holding circuit to itself at armat re I3I to ground through armature I22. Armature I32 operates at this time but performs no useful function. The calling line is now extended through springs I42 and I43 to link conductors 21 and 28 and to key I99. The key I90 is operated to connect the operators telephone circuit G through springs I SI and 192 to link conductors 21 and 28 and thus to substation A.

To determine what service is desired the operator converses with the calling subscriber in the usual manner, the talking circuit may be traced from the operators telephone over leads 3! and 32, armatures IQI and I92, armatures M2 and I43, leads I0 and II and the line I to substation A. Transmission :battery is supplied to the line A through the windings of the relay IIIl.

To extend the substation A to the switchboard Y over one of the two way trunk circuits such as trunk J and assuming that the connection is to be made over trunk J the key 260, Fig. 2, is operated. Ground through spring 26!, armature 23I, and the winding of the relay 246 to battery opcrates the relay 249. The relay 246 closes a look-- ing circuit to itself through armature 2M, disconnects battery from the lower winding of the relay 230 at armature 244, disconnects ground from the upper winding of the relay 230 and connects battery to the upper winding of the relay 230 at armature 243, and operates relay 253 from ground at armature 246. The relay 25!] operates its armatures but has no function to perform at 8.. this time. A circuit is now closed to the upper Winding of the relay 239 in series with the relay 280, from battery at armature 243, upper winding of relay 230, contacts 222, spring 261, trunk conductor 48, armature 235, winding of relay 289 to ground. The relay 230 operates its armatures, closing a holding circuit to the relay 259 from ground through armature 233, armature 25I, winding of relay 252 to battery, and closes a circuit to the lamp 2" from ground through armature 232, armature 245, spring 2 54, lamp 21 I, and lead 33 to battery. The lamp 21I lights indicating to the operator at switchboard X that the trunk line to the switchboard Y has been seized and that the operator at that switchboard has not answered. The substation A and the operators telephone circuit are connected to conductors 21 and 28 as previously described. The operation of the key 260 extends them, through springs 282 and 263, condensers 285 and 286, contacts 222 and 224, springs 261 and 268, and trunk conductors 40 and 4|, to springs 29I and 292 of jack 290.

The relay 28!) operates in series with the upper winding of the relay 23!} over the circuit previously traced and lights lamp 295 from ground through armature 28I and armature 281 to battery over lead t4. The lead 64 terminates in an auxiliary signal circuit such as F, Fig. 1. The lamp 295 lighted, indicates to the operator at the switchboard Y that a call is waiting on the trunk J.

The operator at the switchboard X may now restore the key I93, Fig. 1, to disconnect operators telephone G from the trunk line and allow the calling subscriber to pass information directly to the operator at switchboard Y when she answers or the operator may leave key I operated and either pass information to the operator at the main exchange or supervise the passing of information .by the calling subscriber.

Assuming that the operator at the switchboard Y answers with cord K, Fig. 3, the plug 38I is inserted into j-ack 290, Fig. 2, closing a circuit from ground through the winding of the relay 285, jack sleeve 293, sleeve of the plug 38I, armature 32I, armature 326 to battery through the winding of the relay 330. The resistance of the relay 285 is high enough to prevent the operation of the relay 333 at this time and as the winding of the relay 328 is short circuited by armatures 32I and 326 no operation takes place in the cord circuit K at the time the plug 33I is inserted in the jack 290. The relay 285 operates over the circuit previous-1y traced, opens the series circuit to relays 28B and 236 at armature 286 and extinguishes the lamp 295 by opening its circuit at armature 281. The relay 280 releases and disconnects ground from armature 28I. The relay 230 releases and extinguishes lamp 21I by opening its circuit at armature 232 thus indicating to the operator at switchboard X that the operator at switchboard Y has answered.

When the plug 38I, Fig. 3, is inserted in jack 290, Fig. 2, the trunk conductors 40 and II are extended over the plug conductors to the windings 388 and 389 of the repeating coil and these windings are connected through condenser 386 thus completing a circuit from the substation A or the operators telephone G which are connected to trunk conductors 4B and 41 over the circuit previously traced. The upper winding of the relay 325 is bridged across the condenser 386 but as there is no return path for the battery connected to trunk conductor 40 through the upper 9 winding of the relay'flll-the relay 325 'is' not energized. "The op'eratbr at switchboard Y thenoperates key-tit closing'acircuit from battery through the lower winding of the relay- 359, spring 314, lead 54, armature MB. Fig.4, and-armature M to ground and connectinglead'fl through spring 313 tQ a-rma'ture 354. The-other armatures of key 818 are also operated at this time but perform no useful functi'on. The relay-'35fl -operates, closes a holding circuit for-'itslf fmm battery through its upper-winding; armature 354; spring 313, lead '53, winding of relay Mi -and armature M5 to ground, armatures- 352 and'356 close acircuit for voice currents through repeating coil windings '39I and 392 and condenser 38-lfin-series, over leads -56 and st-and armatures 443 and M4, to the operators telephone M. *The operator at switchboard Y can now talk to the subscriber at substation A and by means of the other end of the cord terminating in plug 391 can extend thecon- -nection to an-y one-of the lines such as the lines N, P or-R terminatedon the switchboard Y.

As described abovethe relay445, Fig. 4, is energized in series with the upper winding-ofthe relay 350. The relay MF-in operating disconnects lead '54 from ground atarm'ature446 which prevents the'operation of therelay 350 in any other cord circuit in the positionand disconnects the lead 52 from 'the -operator-s'-telephcne at armature 441 which prevents the operators talking circuit from being disabled-if the key' 393in=any cord circuit is operated.

After having completed the services requested by the subscriber at' subs'tationlA 'the'operator at switchboard Y may disconnect from the cord K by restoring the key 3J0 epen'ing the circuit to the upper winding of the relay 35fl-at spring 3l3. The

relay 350 releases-and disconnects the operators telephone, M, from the-cord K- at'armatures 352,

353, 355 ahd 356. 'Therelay Ifi-also restores at this time and connects ground'to' the lead 54, s'o that the common equipment L'is in condition-to operate with any 0f "the more "circuits in the position.

When the calling subscriber replaces the receiver at the substation A the rela 1 l I 0, Fig. ;1,

' releases, opens the circuit 'to-the relay I20 and short circuits the relay I30 -at-arn'1ature 'I'I'I, and

icloses a circuit to tne-lampn-clrromgroan -at "armature I l2,'thro'ug h armature I32 =and 'spring M4110 battery overlea-d 33. The' lamp' IM lights indicating to the operator at siiiitcliboardX that the connection s'hould-be releajsed. The relay l3fl releases, opens its holding circuit at armaturefIB-I, opens the circuit to larnpl-Bl'at' arinature 132. The relay I26 is slow torelease but-shbrtly'after vits' circu'it' is-opened atar'maturei l I the relay "1:20 releases, removes the short circuit from the :windingbf-the relay 130 l at armature I2 I and disconnects ground from lead I2 at' armature Iii-3,

allowing the calling switch train' to release.

key-260 is restored the circuit to rel yed-0 1s bpnedat spring 26L The relay 240 releases,

disconnects battery from the upper winding of the relay 230, connects ground to the up eevvmdmg of the relay 23!}, connects battery to the ''lower winding of the relay 23Il,and opens the circuit'to the relay25t which -'-is slow acting and remains operated for "a short time after its circuit is opened. -'-l l"circuit 'canjnow be traced from 'battery through resis'tbr '2-'I4,"a'rI nature 244, lower winding--of-re1ay 2 50, contact 2-24, spring 268; lead 5M, spangeezment conductor of plug 38 I, winding r389; armature 332, upper winding of relay325, armature 39, winding 388, upper conductor of plug smearin 294, -lead=4ll, spring 2% 'I,-contact 222, up er winding' of Y relay 23%, and armature 2 gre'und. Therelay 230' operates, closes a circuit'to-therelay' Z'BO, which because of its slow ates in series with' the relay-2538 over the circuit previously traced and opens the short circuit to thew'indingcf therelay 32Ilat armature 326 thus energizing therelay 320 in series with the relays 33!) and 283.5 over the circuihpr'eviouslytraced.

The rela -32c 'operatesand closes a circuit from roundthrough the armature 322 armature 333, and "lamp 382 to battery. "The lamp 382 lights,

' indicating :to'the operator atswitch-board Y that "theftlllllk J'has been disconnected at switchboard T0 disconnect, the operator at switchboard Y removesjthe plug I331 froin'the 'jack 29!) opening the circuits tothe relays320,'325, 2B5, and'2 30.

The relay releases and opens "the circuit to the lamp-382' at "armature 332 which extinguish'ed. ""Iherelay 325 releases and short circults the winding of relay 32E] 7 at armature 326. The relay"j 285 releasesconnects the lamp 295 'throughainiatureltl to armature 28I, and connects the-winding of the relay 23B through armature-285 to the lead '40. The relay 23B releases and at'ai'inature 123-2 opens the circuit to the lamp .213 .Whi'chis extinguished, and at armature 233 opens .the circuit to the relay 2553. which shortly thereafter releases. The trunkJ is now available to calls originating at either switchboard. I

Assuming now that both switchboards are attended and that the operator at switchboard Y hasanswered one of the lines or trunks terminating -on the switchboard with plug 38I, has

connectedthe operators telephone M to the cord circuit K --by--rneans of' the key-310 and the relay 35!! :as-previously described, and finds that the calling subscriber-desires -:a connection with a 65 subscriber in the automatic exchange. The plug 359? is inserted in the jack +290 completing a circuit fro'm --battery through the winding of the relay'fidm-armature 346. armature 382, lower conductor fofiplug I391, spring "293, and the winding of the relay @285 to ground; The -resistance of the relay 285' is high-enough to prevent the operation of the rel-aye lll' b'ut the relay 285 operates, disconnects'rthe'relay #285 from the lead 40 at armature'236;and"disconnects the lamp 295 from the-armature 28I at :arm'atu're" 2.81. ',;A circuit is 1 1 also completed to the relay 345 in series with the relay 230 which may be traced from ground through armature 243, upper winding of relay 230, contact 222, spring 251, lead 40, spring 29!, upper conductor of plug 391, armature 353, lead 58, back contacts associated with spring 45I, ar-- mature 434, lead 56, armature 352, repeating coil winding 39I, armature 34I, windings of relay 345, armature 336, armature 36I, armature 342, re

' peating coil winding 392, armature 356, lead 51,

armature 435, back contacts associated with spring 452, lead 59, armature 355, center conductor of plug 391, spring 292, lead 4|, spring 268, contacts 224, lower winding of relay 239. armature 244 and resistor 214 to battery. The relay 345 is a polarized relay which operates when negative battery is connected to its right terminal and positive battery is connected to its left terminal, and which releases on open circuit or when positive battery is connected to its right terminal and negative battery is connected to its left terminal. As negative battery is connected to the right terminal and positive battery to the left terminal over the circuit previously traced, the relay 345 operates, closes a circuit from 3:

battery through lamp 398, armature 343 and armature 341 to ground causing the lamp 398 to light, and at armature 346 opens a short circuit to the winding of the relay 360. As the key 310 is operated the winding of the relay 350 is short circuited at spring 315 so the relay 369 cannot operate at this time.

The relay 233 operates in series with the relay 345 over the circuit previously traced, closes a circuit from ground through armature 232, arma- 2 ture 245, armature 252, lamp 212, and lead 33 to battery in auxiliary signal circuit F causing the lamp 212 to light and signal the operator at switchboard X, transfers armature 23I from the winding of the-relay 240 to the winding of the relay 220, and connects ground through armature 233 to armature I. The operator at switchboard X answers by operating a connecting key and a talk key associated with one of the connecting links in the switchboard. Assuming that the operator answers on the link associated with key 250, the key 260 is operated and a circuit is closed from ground through spring 26I, armature 23I, armature 242 and the winding of the relay 220 to battery, the trunk conductors and 4| are extended to key I90 through the condensers 215 and 216, and the springs 252 and 263, and a circuit is prepared for the lamp 21I through spring 264. The relay 22!! operates its armatures,

reversing the direction of current flow over the 4 trunk conductors 40 and 4| by means of armatures 22I and 223 and their associated contacts the effect of which will be described later, disabling the lamp 213 at armature 226, and operating the relay 250 from ground through armature 225. The relay 250 operates, extinguishes the lamp 232 by opening its circuit at armature 252, and closes a holding circuit to itself through armatures 25| and 233. The reversal of current over the trunk conductors 40 and 4|, energizes the 12 tors 40 and 4| and to the cord circuit K at switchboard Y. Assuming that the operator at switchboard Y has not disconnected, by restoring the key 313, a talking circuit is completed between operators telephones G and M. The operator at switchboard X determines what service is required by switchboard Y and can extend the connection to a subscribers substation such as substation A in the automatic oflice over an outgoing trunk such as trunk E. Assuming that the trunk E is used for this purpose the key I19 is operated closing the circuit to the line switch LS over lead I3, contacts associated with spring I6I, left winding of relay I50, spring I15, contacts asso ciated with spring I62, and lead I4. The line switch LS extends outgoing trunk E to a selector such as SEL in the well known manner and the operator at switchboard X may then extend the connection by means of the calling device which is connected to the trunk by the operation of the key I60. The operation of the key I60 disconnects the operators telephone G and the trunk J from the automatic switch train at the contacts associated with springs IBI and I02.

After operating the calling device to cause a selector and a connector to extend the connection to the substation A, the operator at switchboard X restores the key I60 disconnecting thecalling device from outgoing trunk E and reconnecting the left winding of the relay I50 to the leads I3 and I4 by means of springs I6| and I62 and the contacts associated with them. The operation of the key I10 which connected the left winding of the relay I50 to leads I3 and I4 also connected leads I3 and I4 through springs I13 and I14 and springs 262 and 263 to leads 40 and 4|, closed the circuit from battery through the right winding of relay I50 to ground at spring HI, and connected the lamp I 8| through spring I12 to a contact on the relay I50. The relay I50 is a polarized relay and its windings are aiding at this time so that it will operate and light the lamp I8I from ground at armature I5| through spring I12 to battery over lead 33.

The operator at switchboard X now restores the key I disconnecting operators telephone G from the trunk at springs I9I and I92. When the receiver is removed at the substation A the connector reverses the direction of current flowing over the leads I3 and I4 causing the relay I50 to release and extinguish the lamp I8| by opening its circuit at armature I5| to indicate to the operator at switchboard X that the call has been answered.

The operator at switchboard Y will usually disconnect immediately after the operator at switchboard X has been given the information necessary to complete the connection by restoring the key 310, thus allowing the relays 350 and 445 to restore as previously described.

A talking circuit may now be traced from the substation A, through connector CONN, selector SEL, and line switch LS over leads I3 and I4, contacts associated with springs I6I and I62, springs I13 and I14, leads 21 and 28, springs 262 and 263, condensers 215 and 216, contacts 222 and 224, springs 261 and 268, trunk conductors 40 and 4|, springs 29I and 292, upper and center conductors of plug 391, contacts 351 and 358, repeating coil windings 39I and 392, and the condenser 381. Voice currents developed in this circuit induce similar currents in the windings 388 and 389 of the repeating coil which are connected in series through condenser 386 and these induced currents are transmitted over the upper and center ween-we :13 COHIZIHUKOYSOf tl'feiplugiitaI tu thelineeonductors andfN 'o'fi'wlinecircuitasuch as circuit-N, with which;.thecp1ug' 381 hasibeen: connected and=over thelconductors N and. N to thee-substation or other; equipment connected: thereto. Likewise voice: hurrents developed =inthe repeating coil windings 388 :anda BBB by the' talking instrumentalitiesrrassociatedrwith=fthe linedlo which-the 'plug SM-hasibeen connected induce similancurrentsin the windings 38 I JancU3QZ-Which are transmitted-to 1 ithesubstaktion A over the circuitipreviously tr-aced.

When the-:receiver is-replaced at the substation Aiitheconnector CONN changes-the direction of the: current flowing over-leads l 3 and M pausing lamp l'fi l from ground at armature-15L The -1amp= I81 lights;.-indicating to the operator at switchboard XEthat-the substation Ahas been =disconnected. The operator at switchboard-v X then =restoresathei-key I110, eXting-uishingthe lamp l'8l by opening its circuit :at spring 412, disconnects the bnidge: of \the left winding --0f the relay 1-50 ifrom the leads laend; :M to allow the automatic switches to release, opensthe circuit to the right windingwofsthe relay 1-58 atspring 'FH and disconnects f-romithe =1eads 21-and=28 at springs 113 and 414-. The relay'lfiflreleases-when the-circuit to=its windings'are opened:at-the springs 0f the key lloebuteperformsnofunctions The operator :at' theswitchboardX thenrestores-the key 266 -ripeningfthe circuit to the-relay-220=at spring- 26 I and disconnecting' the leads zl and 28 from the trunkrJ at-springs 262-and-263. The relay-220 releases reverses thedirectioxrof thecurrent flowingover'trnnk conductorstfl andM at-a-rmatures '22-] and disconnects ground from the windings-of the relay Bio -at armature J25, andcloses theicircuit from battery through lamp*213,=ar-ma turezzfi, armature 252,=armature 245 andarmature 2-32 to. ground Thelamp 213.-1ights indicating to the-operator-at switchboard X that the trunk .J v-has notlbeenreleasedeat. the switchboard windings: of.-the ipolarized: relay 345 in cord Kw arev now energized in the direction for .operatingsthe rela-y' by the currentifiowing over trunkeconductorstfliand 4L The.re1ay 3 45 operating closesa circuit from'ground througharmature 3M; armature 343,- and-lamp -3 984;oloattery, end-opens the shorteircuit around the winding of the relay 359 at armature -3'56 The lamp 398 F lightsindicating tothe operatoratlswitchboard Y that the trunk Jhaslbeendisconnetited at switchboardX. The relay'fifill is now energizedover a circuit whichmaybetracedfromIbattery through the winding of the relay'ii'tt the'winding o'ffthe relay '55ii1lower conductor of .plug 397', spring'2'95 throug'h'the'windingofirlay 'ZSS'to ground. The rlayBSDl operates, opens a part ofthe'incomplete short circuit for. its winding at armature 362; connects the lamp 3 gsthrough "armature 363" to ground'through armature 33?;an'd opensthe short circuit around thelower' winding of the relay 335 atarmature 3'51; The-lower windingoftlierelay 335 h now energized in series with the relay 345 and the: re1ay"2 30 -'over-the-circuit' previously traced. The relayfiir operates, opens a part of the incomplete short circuit to its lower-Winding at "armature Set; and disconnects ground from armature 331, thus placing "the circuit for "the lamp 398 'entirelyundercontrol of the relay 3'45.

The operator at the "switchboard Y "disconnects from the trunk d by removing the plug "391 from the jack? 9h-='opening 'theci-rcuit 'to therelays e rs: ethane 231i a t-springs zetand e2 andopenmgthe circuitto the -relays sfilranrzw at-sprin'g iii) 5 opening the circuit to the relay Z EB-at'a'rmature a'nd eiitinnisliing the Ia'mp 273 px opening i-tsi oircuitat; armature 2-32. The relay "if llieleases s-hor tly a' fter'its circuit is openedat armature- 2%- connect's armature 2'51 from its left terminal, ari'd connects armature 2 5 2 to the lamp 2%; Lamp ZJB' bei'ng extingui'shed indicates to the operator a't' switchboard X that the 'truiik J has been disconnected at switchboard Y. The trunku ienow at-"normalantravailable-for useon ather connections.

:hssmning now that the switchboard X is unattended and that the operator before leaving the switchboard operated the switching "keys, siich -as'key-265, in the two way trunks, such as two way 'triink U, and *that the-subscriber at the' subs'tation A wishes to extend a call tothe switchbcardY. When the receiver at the substationhisremoved the substation'A is connected by "means of the line 'I and its individual line :5 switch 'over a trunk line such-as line "4 toaselecto'r such as selector SEL. Assuming that the selector SELha'sbeen seized it will step its wipers to thelevel associated with incoming trunks such as-trunk D in response to the operation of the callingdevice at the-substation A and will'autoinatically search for an idle trunk; Assuniihg lay' l lfd-willbe-energized in series with the "calling substation previouslydes'cribed. The-relay W0energizesthe'relay [20fr0i'h ground'a't armatureWQL'anii connects ground through armature H 2 armature I33 tothe lamp [82. Kbttiybut-fikey, I101; shOWn, is provided if! the auxiliary signal circuit F forthe disconnection (if battery from the lampssuchhs lampl'B2, when the switchboard X is "unattended. However, *the lainp' l3 2'has no functionto perform in the trunk circuit!) when the switching key26 5 iso'pe'rated, The relay [26 operates its arma- 5 titres,"arrrlatiires7 21 ahdl22 haviiig ho'fiinction t'o'perfo'rm. Armature [23 connects ground over lead [2 "toselector to hold the automatic switches. ahdconir'ects ground through spring- 266 over flead ltito the B. C. O. relay ofthe line switchdisto cl-ear the leads [3 "and I' l; which haveibee'nlcorinectedlthrough springs as: and 2'68 to trunk ednducto'rs is an'clt, of attachments and"tl'iiis 'rfeventranyinterference with this connetionb'y'the line "switch LS. Thefground on lead lr'alsoflmak'es. thetriu'nk Dinacces'sible to dtherselectors. There lay '2!!! is energized from groundat armature 124 through springfzfis and operates its armatures. Lead is is connected throtigharmaturezirto condenser 275, lead "I I is connected through"arrnature 215 to condenser 27-5, trunk conductor dfi 'is 'connect'ed' through armature 2 l's'an eoiita'cts 222 "to the up er windiiigor-remy 2 st, trunk c'onductor the connected throu armature t ltanqmntacts '2'24; to the lowertiiindih gfif the *Tel ay" 230; 'arid 'the relay 2W0 isenergized from ground through armature H2. The relay 24!! operates its armatures, the armatures 241 and 245 having no function to perform. Armature 242 opens part of the incomplete circuit to relay 220, armature 243 disconnects ground from the upper winding of the relay 230 and connects said winding to battery through resistance 214, armature 244 disconnects battery through resistance 274 from the lower winding of the relay 238, and the relay 258 is energized from ground at armature 246. The relay 250 operates its armatures, armature 25E connecting the winding of the relay 259 to armature 233 and armature 252 being connected through armature 226 to the lamp 273.

A circuit may now be traced from battery through resistance 2T4, armature 243, upper winding of relay 238, contacts 222, armature 2l3, trunk conductor 48, armature 238 and the winding of relay 2% to ground. The upper winding of the relay 238 and the relay 289 are thus energized in series. The relay 238 operates its armatures, which perform no useful function at this time. The relay 28!! operates and closes a circuit from battery over lead 84 through lamp 295 and armature 281 to ground through armature 28L thus lighting the lamp 285 to signal the operator at switchboard Y.

The operator at the switchboard Y answers by inserting a plug, such as plug 38I, of a cord circuit, such as cord K, into jack 290. Assuming that cord K is used in this case, the relay 285 is energized over spring 293, lower conductor of plug 38i and the winding of the relay 330 as previously described. The relay 285 operates its armatures, armature 285 opening the series circuit to the relays 280 and 23D, and armature 287 extinguishing the lamp 295 by opening its circuit. The relay 2% restores and disconnects armature 28! from ground. The relay 23D restores its armatures which have no efiect on the performance of the circuits at this time. The insertion of the plug 88I into jack 298 connects the upper conductor of plug 38! to spring 29I and the center conductor of plug 38I is connected to spring 292. A talking circuit can now be traced from substation A over line I, through the line switch individual to line I, over trunk line 4, through selector SEL, leads Ii! and II, armatures 2H and 2I5. condensers 215 and 216, contacts 222 and 224, armatures 2I3 and 2I4, trunk conductors 49 and 4|, springs 29I and 292, upper and center conductors of plug 38I and repeating coil windings 388 and 389 in series with condenser 385. The upper winding of the relay 325 is also connected in series with the repeating coil windings 988 and 389 but does not operate at this time as there is no power source connected to the circuit. The operator at switchboard Y connects operators telephone M to repeating coil windings 39I and 392 in series with condenser 381 by means of talk key 310 and relay 358 as previously described. Voice currents generated at substation A flow through repeating coil windings 388 and 389 and induce similar currents in repeating coil windings 39I and 392 which are transmitted to operators telephone M over leads 56 and 51, while voice currents generated at 0perators telephone M flow through repeating coil windings 39I and 392 and induce similar currents in repeating coil windings 388 and 389 which are transmitted to the substation A over the circuit previously traced. The operator at switchboard Y may now extend the connection and disconnect from the cord circuit as previously described.

When the receiver is replacedat substation-A the circuit to the relay H0 is opened. The H0 restores its armatures, the circuit to the relay I29 being opened at armature III, and armature H2 having no function to perform at-this time. The relay I28 restores its armatures, armatures I'2I and I22 having no function to perform. Armature I23 disconnects ground from the lead I2 to release the automatic switches and from the lead E5 to release the B. C. O. relay of the line switch LS. The circuit to relay 2 I 0 is opened at armature 524 permitting the relay 2"? to restore its armatures. Leads I8 and II are disconnected at armatures 2H and 2I5 from condensers 215 and 216 respectively. Armature 2I3 disconnects condenser 275 and the upper winding of the relay 238 from trunk conductor 49. Armature 2 I4 disconnects condenser 216 and the lower winding of the relay 232 from trunk conductor 4|. The circuit to the relay 240 is opened at armature 2I2. The relay 248 restores its armatures, armatures 2M and 245 having no function to perform at this time. Armature 242 is connected to the winding of rela 220, armature 243 disconnects battery from the upper winding of relay 232 and connects said winding to ground, armature 244 connects the lower winding of relay 238 to battery through resistance 214, and armature 248 opens the circuit to the'relay 250. Shortly after its circuit is opened the relay 250 restores, disconnects armature 25I from its winding and connects armature 252 to the lamp 212.

As previously mentioned the circuit to the B. C. O. relay of the line switch LS is opened at armature I23 when relay I20 releases. The B. C. O. relay releases and the line relay of the line switch operates in series with the upper winding of the relay 325 from a circuit which may be traced over leads I3 and i4, springs 28! and 288, trunk conductors 40 and 45, springs 29I and 292, upper and center conductors of plug 38I, repeating coil windings 388 and 389, armatures 33! and 332 and the upper winding of relay 325. The line switch operates and seizes a selector, such as SEL, in the well known manner causing ground to be returned over lead I5, through spring 265 to lead I2 to make the trunk D inaccessible to other selectors. The relay 325 operates its armatures, armature 325 opening the short circuit around the winding of the relay 328 and armature 321 disconnecting ground from part of an incomplete circuit for lamp 382. The relay 329 is energized from battery through the winding of relay 338, winding of the relay 32!], lower conductor of plug 38!, and spring 293, through the winding of relay 285 to ground. The relay 320 operates, armature 32I opening a part of the incomplete short circuit to the winding of the relay 328, and armature 322 closing a circuit from ground, through armature 333, and lamp 382 to battery over lead 64 which is connected to an auxiliary signal circuit similar to auxiliary signal circuit F of Fig. 1. The lamp 382 lights indicating to the operator at switchboard Y that the trunk J has been disconnected at the automatic ofiice.

The operator at the switchboard Y disconnects from the trunk J by removing the plug 38I from the jack 298, opening the circuit to the relays 320 and 285 at spring 293, and opening the circuit to the relay 325 at springs 29I and 292. The relay 320 restores, closes a part of the incomplete short circuit to its winding at armature 32I, and extinguishes the lamp 382- by opening its circuit at armature 322. The relay 325 mstores, short circulting thewiudingof the relay 320 at armature 326, and prepartirlg a circuit to the lamp 382 at armature 321; The relay 285 restores; connecting the relayzsoao trunk conductor 40 at armature iflkandcomiecting armature 287 130 the lamp 295'r The holding bridge for the selector: which had been seized by. the line'switch Us is also opened at springs 29! and :zaz w-nenl the plug 3814s removed from the-jack 290. The selector: and the line switch Ls release and ground which has been extended over lead vl through sprmg 26'5 to-lea'd l2 -is dlscohnected. TrunkD is now accessible to thevselectorsiand thetrunk J has restored to normal and may be seized at either endfor establishing other: connections.

Assuming now'that the operator at switchboard Y has answered a call onone of the lines-such as the .lineN withthe :cord K,- that the plug 38'! has been connected-with the line N, that y the operators telephone M has beenconnected to repeating coil windings 38! and 392 as previously described and that-the connection is to be extended to the substation A in the automatic ofiice 'overthe-two way trunk- J. The operator at switchboard Y: inserts the plug 39 into jack 2% closing a circuit from battery through the winding of relay mar-mature 346, armature 362, lower conductor of plug. 391,, and spring 293 to ground throughthc'winding of relay 2-85. The resistance of the winding of the relay 285 is high enough to prevent the operation of the relay 340, however the relay 285 -opcratesits armatures disconnecting the relay. 2801mm trunk. conductor 46 at armature 286, anddisconnecting armature 28'! from the lamp 295; A circuit is also closed now to the winding of the polarized relay 315 which may be traced through armatures 3B] and 382, repeating coil windings 3'9! and 392, armatures 352- and 35B, leads 56 and' 51; armatures 834 and 435, contacts 153* and #54, leads 5!! and 59; armatures 353 and 355', upper and center conductors of plug 397, springs '29! and 292, springs 261 and '2'68'over leads l3'and to ground'and battery at the line switch LS. The direction of current flowing in this circuit'is such that the relay 345 operates its armatures, closing a circuit from ground through armature 341; armature 343 and lamp 398 to battery, and opening part of a short circuit around the winding of the relay 365 at armature 346. The lamp 398 lightsindi eating to the operator at switchboard Ythat the line switch LS has been seized. As the talk key 310 is operated the winding of the relay i'i'tfl is short circuited by spring 315 and the relay 360 cannot operate at this time.

The line switch operates in series-with the windings of the'relay 3E5 extendingIthe connection over a trunk line such as line [to a selector such as selector SELL Assuming that in this case the connection is extended over trunk line 4 to selector SEL' the line-relay of the-selector SEL is operated in series with thewindings ofthe relay 345, ground is'returned over the trunk line 4 to the line switch LS to hold it operated and from the lineswitch overload l5, andspring 266 to lead ii to maketrunk D and therefore trunk J inaccessible to the selectors, and dial tone will be forwarded to operators telephone M over the circuit previously'traced. The opera tor at switchboard normallyhave been ash visedthat the switchboard X isunattendecl-and upon hearing dial tone will operate :the calling device" S tccuti'tue: code required to step thesciectcrSEL tozacrsuch :as connector GQNN, which wil-l -aasmed' to be the connector uscd in thiscaseyandito step the connector CONN to the line. l tc' which substation disconnected: y

when the'callinzdevicms is oii normal, ground from the:callingtclcvlrze through the Winding of thereby '8 towbattery energi'zes" the relay 4-40 which-operates and'ac zitaannature: is attracted the pair o sprincsireprcsented by the armature 442 are closed mst conuectmgithe condenser 415 to theleads -fi and 55 sommirzuze the noise caused by trausrerlang liromthcholdirrg bridge through the windings-or fine-retry" 345' to' th'e impulsing bridge in thecalllrzguevlce S. "ll-herelay 440 continues tcopemtem tullandthus all of the springs oitherelaymremctuated; Armatures 4-43 and 444 disconnoctthe opcratori s' telephone M from the leads WEflfi'i-TIBQWGHVMY: Armature 44'! extends grouzxdirom the calli'ng deviceto the windlng or the relayrflo -wnieh operates and' as its armatureisattracted-impairs cit-springs represent'cd -:by armaturesifirand l 3'3 are-closed first.- Qne side or the:.-iinpulsmg bridge in the calling device sis ccnnectedsthroughtspring 461; resistan'cefl't l; armature-I32; contestant-'4; lead 59, and armatureiui tothc-centcrconductor or plug 397 and theother slde:orthcimpulsing bridge is connectedtnrougnarmatureflh contacts 453, lead 58:, andarmaturelfl to thc upper conductor of plug-e91; 'frne'imerelayfiortheautomatic switch ccnn'ecteditc tnmksi conductors: '40 and M and through jack spring! I 'andflstto the upper and center conductors oi plug: 391 is momentarily held by. the bridaeoithcwindingsof the'pol'arized rela :uivimmultiplezwlth the: resistance 474 and the impulsingqbridte"inflcailingdevice S in series; The relay 'flll ccntinues-toroperate in full and thus all oi the springs orthe relay are actuated. The bridge or 'the windinis of polarized relay 345 is disconnected: from the impulsingbridge and iromtheplusiifl -athrmatures 434 and 435 and the:resistance'fll isshortcircuited at armature 43L The linc relaysoflthe-automatic switch connected 'to -the-cord-K-is thus under control of the impulsingbridge;and will cause the switch to step in the-welllmown manner'in response to im-' pulsesgenerated in the'bridze by thecalling device-S. After eachdigitthe ground may be disconncctedat the device and reconnected shortly beiore-the'lnext digit is to be transmitted. If the interval between digits-is-long enough relays 430 and 410 may release and transfer the circuit for the line relaysoi thc automaticswitch connectedto the cord the-windings of polarized relay'lfie However, afierthe -last digit has been transmitted and-= the balling device S has restored to normaL-thercircuits to relays 43 6 and ll will-beopened for along; enough interval to allow-them to release. The sleeve on the-relay Mb makes-it relativelyslowto release sothe relay 4% restores its armaturesfirst. Armature 43! first removes theshort circuit irom the resistance 414, armatures: 434 anlzhh'iitherrcoxmect the repeatingcoil windings I and 382-and the windings of the polarized relay- 345 to the 'automatic switch connected K; stud finally 'armatures 432 and' 433 disconnect 'the- 'impulsing; bridge from the-cordcircuit Thc rclay 440; in restoring first disconncctsthewinding or the relay 4% from the callixxgvdevicc-atarmature 444, then connects the operator's p to :-'cord K at arm-atureai-fli and lfl' and vfinally disconnects the condenser .415 from the cord K at armature1442'. The sequence of the operation of the armatures of relays 438 and. 448 minimizes the noise transmitted to the line N while transferring to and.

from the impulsing bridge;

After the operator at switchboard Y has dialled the digits required to reach substation A the talk key 318 may be left operated until the either ring back tone or busy tone is returned by connector CONN. Assuming that the line |.is free, the operator after hearing the ring back tone may disconnect the operators telephone M from the cord by restoring the talk-key 318 thus allowing relays 358 and 445 to release as previously described. The short circuit to the Winding of the relay 388 is opened at spring 315 when the talk key 318 is restored. A circuit can now be traced from battery through the winding of relay 348, through the winding of the relay 368, the lower conductor of plug 391 and spring 293 :through the windin of relay 285 to ground. .The relay 368 operates, armature 36! opening a, short circuit around the lower winding of the relay 335, armature 382 opening part of an incomplete short circuit around the windingof the relay 368, and armature 383 connecting a multiple ground to the lamp 398 through armature 331. The lower winding of the relay 335is now energized in series with the windings of polarized relay 345 and operates its armatures, opening part of the incomplete short circuit around its own winding at armature 336, and disconnecting ground from the armature 363 and thus from lamp 398 at armature 331 so that the circuit to the lamp 398 remains under control of the polarized relay 345.

When the receiver at the substation A is removed the connector reverses the direction ofcurrent to the polarized relay 345 over the circuit previously traced causing the relay 345 to restore its armatures. Armature 346 closes part of an incomplete short circuit around the windin of relay 388, and armature 341 opens the circuit to the lamp 398. The lamp 398 is extinguished indicating to the operator at switchboard Y that the subscriber at substation A has answered.

When the subscriber at substation A disconnects, the direction of the current for energizing the coils of polarized relay 345 is again changed causing the relay 345 to operate its armatures. Ground through armature 341, armature 343 and the lamp 398 to battery causes the lamp 398 to light indicating to the operator at switchboard Y that the subscriber at substation A has disconnected. n 3

The operator at switchboard Y disconnects from the trunk J by removing the plug 391 from the jack 298 opening the circuit to relays 335' and- 345 at the upper and center conductors of plug 391 and opening the circuit to relay 368 at the lower conductor of plug 391. The plug 381 is also disconnected from'the line N and the apparatus of cord K restores to normal making the cord ready for use on other-connections.

The holding circuit tothe automatic switches is opened at springs 29l-and 292 when'plug 391 is removed from jack 2 98. The automatic switches release and ground over lead l5 and spring 288 to lead 12 is disconnected making trunkD accessible to the selectors. The'cir'cuit to the relay 285 is opened at spring 293 when plug 391 is removed from jack 298 allowing thea'r'matures of the relay to restore. Armature 288 connects relay 288 to trunk conductor 48 andarmature 281 is connected to lamp 295. The two way trunk J is-available for 20 establishing other connections between the auto-i matic office and the switchboard Y.

It may be noted in trunk J that with the key 265 operated the lamp 295 at switchboard Y will not light in response to the. operation of the key 288. The operation of the key 268 operates the relay 248, as previously described, which in turn .operates the relay 258 and connects battery through resistance 214 to the upper winding of the relay 238. The, series circuit to the upper winding of the relay,238 and the winding of the relay 288 .is open at spring .261 and therefore the relays 238 and 288 do not operate. However, should the trunk D be, seized by one of the subscriberslines the relays H8 and 128 operate and the relay 218 is operated from ground at armature I24. The series circuit to'the upper winding of the relay 238 and the Winding of the relay 289 is closed through armature M3. The lamp 21! will be lighted by the operation of the relay 238 and the lamp 295 will be lighted by the operation of the relay 288. Both lamps will be extinguished when the relays 238 and 288 release after their circuit is opened by the operation of relay 285 in response to the answering of the call at switchboard Y. The release of the connection and the guarding of the trunk against intrusion until both ends have been disconnected are entirely under control of the subscriber line through trunk D and the switchboard Y. When a call is originated at switchboard Y on the trunk J the relay 218 is not operated and hence the key 288 can have no efiect of performance of the trunk J or the associated apparatus.

When an operator is again assigned to the switchboard X the switching keys, such as key 265,'inthe two way trunks, such as trunk J, are restored and battery is connected to the lamps, such as I81, I82, 211 and 212 through auxiliary signal circuit F. Connections between the switchboard Y and the automatic oifice will then be routed through the connecting links on the switchboard X as previously described.

Having described myinvention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In a telephone system, an automatic exchange, said exchange including a plurality of connecting links and a plurality of incoming trunks and a plurality .of outgoing trunks, an automatic switch individual to each outgoing trunk, a second exchange, a plurality of two way trunks connecting said exchanges, means including any one of said links for establishing connections from said automatic exchange to said second exchange over any one of said two way trunks through any one of said incoming trunks, meansincluding any one of said links for establishing connections from said second exchange to lines in said automatic exchange over any one of said two way trunks through any one of said outgoing trunks including the automatic switch individual thereto, and switching means individual to said two way trunks for enabling connections to be established from said automatic exchange to said second exchange over an individual one of said incoming'trunks and an individual one of said two way trunks independent of said links, and for enabling connections to be established from said second exchange to said automatic exchange through the automatic switch of an individual one .of said outgoing 2r trunks and said individual-two my. trunk inde pendent of said links. 2. In a telephonesystem,anoperatorattended switchboard in one exchange and-1 an operator attended switchboard :in anantomat-ic-cxchange, incoming trunks .andoutgoingtrunks-in said :last switchboard, a two way line connectir-ig said switchboards, meansafcnestablishmg interexchange. connections. over said trunk. linev and any one ofsaid incoming tl'illIkSDl'rB-HY'ODfiOf said outgoing trunks with thev assistanceot 012-.- erators at saidswitchhoards,.and...means in'said automatic exchange foroperatively associating said trunk line with one-ofsaidincoming-trunks and with-one orsaid outgoing. trunks so that.in-. terexchange connections may: be, established thereover. with the assistance. of. an operator at said first switchboard. I

3. Ina telephone-system, automatic ex-.- change including. subscribers; lines, anvoperator attended switchboard; automatic. switches for enabling connections;v to be established; between said subscribers lines and; said: switchboard, a second exchange,- a trunknl-ines-connectingsaid exchanges, operator,v controlled means. in said switchboard for extending said connections; to. said second exchangeoyer. said; trunk line, and switching means in said switchboard for. operas tively. associating said trunk; linegwith: said: auto! matic switches so that-connections may-be established between said subscribers? lines. and; said second exchange independent ofgsaid operator.

4. In a telephone system, anautomatic; exchange having subscribers lines andrautomatic switches, an operator"- attended switchboard thereat, a two waytrunlt line. descend-exchange, meansincluding more. than one of said automatic switches for enabling said, operator to establish connections over said trunk line between said second exchange. and said a subscriber lines,

and switching; means .in,-said switchboard for connecting said trunkline with one-of said automatic switches to enable .connectlonsto .be. established between said second.exchange-andsaid subscribers lines independentofrsaid operator.

5. In a telephone system, automatic switches, a firstswitchboard, a secondswitchboard, a two conductor trunkconnecting said switchboards. a signal for said trunk in each switchboard, a'key in said trunk, means for'operating either the signal at the firstswitchboard. oroneof said automatic switches. in responseto theclosure of said trunk conductors at thesecond switchboard depending on whether said ,keyis normal or op.-

erated, means including only one of. said trunk conductors for operating the signal at the second switchboard, said last. means operative. either under control of saidfirstswlthboardor under control ofany one of aplurality of saidauto matic switches depending on whether saidkey is normal or operated;

6. In a telephone system, an. automatic ex change, subscribers lines, a first switchboard, in-

coming trunk circuits in 'saidtswltchboard accessible to said subscribers lines, asecond switchboard, a two way two conductor trunkconnecting said switchboards, a signal for-said'trunkiateach switchboard, a key,'connecting means-in said first switchboard for-connecting anyone of saidin- 7 trunksiby one orsaid subscribers. lines depending cn whether said key is normal or operated, outgoing trunks from saidfirst switchboard to said automatic exchange, a line switchfor each outgoing trunk, either means ior operating the signal at said first switchboard or the line switch or an individual one of said outgoing trunks operative inresponse-to the'closure of the two conductors of said-trunk at said second switchboard depending on whether said key is normal' or operated, and means'including partor'said connecting means for connecting said two way trunk to any one of saidoutgoing trunks, the line switch of said one outgoing trunkbeing operative in response to said last means.

7. Ina telephone system, twoswitchboards; a two conductor trunk connecting said switchboards, a line relayand a line signal at each switchboard, the line relay at one of said switchboards operative in response-to the closure of said trunk conductors at the other of-said switchboards to operate the line signal at said one switchboard, a key at said oneswitchboard, a controll relay at said'one switchboard-operative -in response to the operation of said key, the line relay at said otherswitchboa-rd being operative over one of'said trunk conductors in response to'the operation of said control relay to operate the-line signal at said other switchboard.

8. In a telephone system, an attendants switchboard comprising a line relay, a line'signal, asupervisory signal, a connecting key and a control relay; a manual swi-tchboard comprising a line relay, a line signal and-a cut-off relay; a two: conductor trunk connecting said switchboards; the line relay at said attendants switch board operative in response to the closure .ofsaid trunk-conductors in-case said trunk is'taken'for use at said manual switchboard; the line signal at said'attendantnswitchboard being operative in response to the operationof said line relay; said control 'relayoperative in response to the operation. of said'connectingkey when said trunk is takenfcruse at saidattendantsswitchboard to F operate the line relays at each of said'switchsupervisorysignalbeing operated in response to the release of the line .relayat saidattendants switchboard, thereafter said last-mentioned. line relay being inoperative in response to the closure of said. trunk conductors.

9. In a telephone system, two switchboards, a: two conductor. trunk connecting said switchboards, a double woundrelay and a battery at one of said'switchboards, oneside of one winding of said. double wound relay. connected to one of said-conductors and the other side of'said one winding. connected to ground, one sideof, the other winding of said double wound relay connected totheother of said conductors and the other side of said other winding connected to the negative pole'of saidjbattery, the positive. pole of said battery being connected to ground, said 'relay operative in response to the closure of said trunk conductors at the other'ofsaid switch-'- boards,- a llnesignal at said one switchboard 0p-.

'76 eratlve in response to the operation of said double wound relay, a single woundrela'y at said other switchboard; one side of said winding being con-l nected to ground and the other side of said winding being connected to said one trunk conductor, a, control relayat said one switchboard, a key for operating said control relay, said one winding of said double woundrelay being disconnected from ground and connectedto the negative pole of said battery for energizing said double wound relay and said single woundrelay over said one trunk conductor in response to the operation of said control relay, another line signal at said other switchboard beingoperative in response to the operation of said single wound relay and a supervisory lamp at said one switchboard being operative in response to the operation of said double wound relay in case said key is operated.

10. In a telephone system, two switchboards, a two conductor trunk connecting said switchboards, signals for said trunk, a cord circuit having signal control devices at one switchboard, meansresponslve to the initiation of a call at said one switchboard and including one of said signal control devices and a relay for establishing a current flow over the two conductors of said trunk to operate a signal thereof at the other switchboard, means responsive to the answering of said signal for reversing the direction of current flow over said trunk conductors to operate said one signal control device, control means responsive to the initiation of a call at said other switchboard for establishing a current flow over one conductor of said trunk, means responsive to said last current flow for operating another signal thereof at said one switchboard, means responsive to the answering of said other signal for preventing current fiow over said trunk conductors, said control means responsive to disconnecting at said-other-switchboard for establishing another current flow over said trunk conductors, another of said signal control devices at said one switchboard operative in response to said other current flow and said relay operative in response to said other current flow to operate a further one of said signals at said other switchboard to indicate that said trunk has not been disconnected at said one switchboard.

11. In a telephone system, an automatic exchange including subscribers lines, a control circuit accessible to said lines, two switchboards, a trunk including a switching key connecting said switchboards, a connecting key for said trunk at one of said switchboards, a signal for said trunk at each switchboard, relays for operating said signals responsive to the operation of said connecting key with said switching key normal, means responsive to the seizure of said control circuit by one of said lines for operating said relays one of which operates the signal at the other of said switchboards with said switching key operated, said last means effective for operating the signal at each of said switchboards with both said switching key and said connecting key operated;

12. In a telephone system, an operator attended switchboard, a two conductor trunk having signals, a relay in said trunk, subscribers lines, automatic switches accessible to said subscribers lines and accessible to said trunkunder control of said operator, means including the two conductors of said trunk for operating said relay to operate one of said signals, a connecting key in said switchboard, means responsive to the operation of said key and including awinding of said 'relay and one of the conductors of said trunk for operatinganother oi said signals, and

switching means in 'said' trunk; said last means being controllable from said subscribers lines through any one of said automatic switches, said relay being inoperative, and one of said automatic switchesrb-eing accessible to the operation of said trunk'in response to said first means in case said switching means is operated.

13."In a telephonesystem; two telephone exchanges, a two way trunk line terminatingin said exchanges, a manual switchboard having a signal and a plurality of automatic switches at one of said exchanges; a line switch having outgoing trunks to said automatic switches, means responsive to. the closure of said trunk line at the other of said exchanges foroperating said signal, and a switch in said trunk line,'said signal being disabled and said line switch being operated for seizing one of said automatic switches in response to the closure'of said trunk line at said other exchange in case said switch is operated.

14. In a telephone system, an operator attended switchboard having connecting links, a plurality of trunk lines,-a plurality of automatic switches having accessto said trunk lines through said connecting links, other automatic switches individually accessible to any one of said trunk lines through said connecting links, and switching means in each ofsaid trunk lines manually operable to allow said plurality of automatic switches to have automatic'access thereto and to connect individual ones of said other automatic switches to corresponding individual ones of said trunk lines with the switching means in said trunk lines operated.

15. In a telephone system, a trunk line, an operator attended switchboard, operator controlled connecting links therein, a plurality of automatic switches having access to said trunk line through said links, other automaticswitches accessible to said trunk line through saidlinks, and switching means in said trunk line operable to allow said plurality of switches to have automatic access thereto and to make one of said other switches automatically accessible to said trunk line responsive to the operation of said switching means.

16. In a telephone system, a trunk line, an operator attended switchboard, a plurality of automatic switches, aplurality of line switches, operator controlled nieans making said trunk line accessible to said automatic switches for making said automatic switches accessible to said trunk line through said line switches, and switching means in said trunk line operable to make said trunk line automatically accessible to said automatic switches and to make one of said line switches automatically operative with said switching means operated whereby said automatic switches are made accessible to said trunk line by way of said one line switch.

17. In a telephone system, a trunk having a plurality of conductors connecting two switchboards, a linerelay and a line signal'at each switchboard, automatic switches at one switchboard, means including the trunk conductors for operating the linerelay at said one switchboard to operate the line signal thereat, switching means manually operative for making said last mentioned line relay inoperative and an automatic switch operative. in response to said first means, and means including theline relay at each switchboard and only one of said conductors for operating the line signal at the other switchboard, said last means effective withor'without said switching means operated.

18. In a telephone system, a two conductor trunk connecting two switchboards, automatic switches at one switchboard, a call signal at each switchboard, means including the two conductors of said trunk for operating the call signa1 at said one switchboard, means for operating the call signal at the other switchboard over a single conductor of said trunk, and means for disabling the call signal at said one switchboard and for making one of said. automatic switches operative in response to the operation of said first means.

19. In a telephone system, a trunk circuit having talking conductors, a plural wound relay, a plurality of signals, means responsive to the closure of said talking conductors for energizing two windings of the relay to operate one of said signals, means for energizing one winding of the relay over one of said talking conductors to operate another of said signals, said last means effective to prevent the energization of said relay in response to the closure of said talking conductors.

20. In a telephone system, a two way trunk circuit having talking conductors, a plural wound relay, a plurality of signals, said relay operative in response to the closure of said talking conductors in response to a call over said trunk in one direction to operate one of said signals, means responsive to a call over said trunk in the opposite direction for energizing one winding of the relay over one of said talking conductors to operate another of said signals, means responsive to the answering of said last call for deenergizing said one winding of the relay, said other signal operative in response to the release of said relay, and said first means efiective to prevent the energization of said relay in response to the closure of said talking conductors.

21. In a telephone system, a trunk having two conductors, a relay, a line signal, a supervisory signal, means for operating the relay over said two conductors when the trunk is seized in one 26 manner, said relay eiTective to operate the line signal, and means for operating the relay over one of said conductors when the trunk is seized in another manner, said relay eifective to operate the supervisory signal.

22. In a telephone system, a two conductor trunk, a relay, a call signal, a supervisory signal, means including said relay for operating said call signal in response to the closure of the conductors of said trunk, and means for operating said relay over one conductor of said trunk to operate said supervisory signal.

23. In a telephone system, a two way trunk line connecting two exchanges, a relay and two signals in one exchange, means effective when the trunk is taken for use at the other exchange for operating said relay to operate one of said signals, and means effective when the trunk is taken for use at said one exchange for operating said relay to operate the other of said signals.

24. In a switching system, a two conductor trunk line connecting two switchboards, a line relay and a line signal at each switchboard, means including the trunk line conductors and the line relay at one switchboard for operating the line signal thereat, and means including the line relays at both switchboards and only one of said conductors for operating the line signal at the other switchboard.

KARIL L. BURGENER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,116,538 Johnson Nov. 10, 1914 2,265,151 Crocker Dec. 9, 1941 2,332,885 Bakker Oct. 26, 1943 2,335,481 Boswau Nov. 30, 1943 

